One of the new features in OS X Mountain Lion is the new AirPlay Mirroring feature. AirPlay Mirroring makes it easy to give presentations, watch Flash videos (Hulu, anyone?) or show off photos from your recent vacation on a TV. If you want to see AirPlay Mirroring on OS X in action, make sure to check out Jason Parker's video demonstration.

One thing that isn't really advertised about the new AirPlay feature on your Mac is the capability to send only the audio from your Mac to any AirPlay compatible device. Meaning, you don't have to mirror your entire display to get the sound from your Mac to your Apple TV.

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Sure, you have been able to stream music from iTunes to your Apple TV for some time now, but what about streaming music from other sources such as Spotify or Slacker? With OS X Mountain Lion, a Mac built in mid-2011 or later, and an AirPlay compatible device, it's now possible.

Remember, you'll need an Apple TV (or AirPlay compatible speaker) connected to the same network as your Mac for this to work.

In order to stream all audio from your Mac using AirPlay, you simply need to change the audio output of your Mac. You can do this one of two ways:

Screenshot by Jason Cipriani/CNET

The first is by launching System Preferences > Sound > Output and select Apple TV.

Screenshot by Jason Cipriani/CNET

The easier method is to hold down the Option key on your keyboard, then click on the speaker icon in your menu bar. You will then see a list of audio output devices, including your Apple TV.

Once you change the audio output to the Apple TV, all audio coming from your Mac will go through the Apple TV, and not the internal speakers on your Mac.

To change the audio output back to your Mac's internal speakers, you can either Option-click on the speaker icon again and select internal speakers, or you can go back into System Preferences and change it there.